#include<iostream>
#include<cstring>
using namespace std;
long long a[21][21]={1},n,m,c1,c2,i,j;
bool a_[21][21];
int xx[9] = {0, 1, 1, 2, 2, -1, -1, -2, -2};
int yy[9] = {0, 2, -2, 1, -1, 2, -2, 1, -1};
int main(){
	cin>>n>>m>>c1>>c2;
	memset(a_,false,sizeof(a_));
	for(i=0;i<9;++i){
		int tx=c1+xx[i],ty=c2+yy[i];
		if(tx>=0&&ty>=0&&tx<=n&&ty<=m){
			a_[tx][ty]=true;
		}
	}
	for(i=0;i<=n;++i){
		for(j=0;j<=m;++j){
			if(i!=0)
				a[i][j]+=a[i-1][j];
			if(j!=0)
				a[i][j]+=a[i][j-1];
			if(a_[i][j])
				a[i][j]=0;
		}
	}
	cout<<a[n][m];
	return 0;
}